67313e1dad
checkIntLiteralFits range-checks a literal against its integer target (builtins + custom widths via intLiteralRange; width-64 types skip — every representable literal is a legal bit pattern there) and diagnoses with the type's range and an xx/cast hint. Wired into the .int_literal arm (covers decls, assignments, call args, struct-literal fields), lowerStructConstant, and globalInitValue. A negated literal now folds to a single constant so -128 range-checks as -128 rather than as an out-of-range +128 intermediate. An explicit xx operand skips the check — truncation stays available on request (cast(T) was already exempt: its value arg lowers without the target). examples/0300-closures-lambda.sx pinned 133 wrapping to -3 through an s3 param — the exact class this outlaws; updated to a fitting value. Found during the fix and filed separately: issue 0113 (negated-literal global initializers rejected as non-constant; pre-existing). Regressions: examples/1156-diagnostics-int-literal-out-of-range.sx, examples/0174-types-int-literal-boundaries.sx.
99 lines
4.6 KiB
Markdown
99 lines
4.6 KiB
Markdown
# RESOLVED — 0112: out-of-range int literal silently wraps into a narrower annotated target
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**Root cause:** the `.int_literal` arm adopted an integer `target_type` with no
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fits-check, truncating at emission width; `globalInitValue` serialized literal
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global initializers raw the same way.
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**Fix:** `Lowering.checkIntLiteralFits` (src/ir/lower.zig) range-checks a
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literal against its integer target (`intLiteralRange`: builtins + custom
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widths; width-64 types skip — every representable literal is legal there) and
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diagnoses `integer literal N does not fit in T (range lo..hi) — use an
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explicit `xx` / `cast` to truncate`. Wired into the `.int_literal` arm,
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`lowerStructConstant`, and `globalInitValue`. A negated literal now folds to
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one constant (`-128` checks as -128, not as an out-of-range +128
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intermediate), and an explicit `xx` operand skips the check
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(`suppress_int_fit_check`) — truncation stays available on request;
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`cast(T)` was already exempt (its value arg lowers without the target).
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Coverage via the shared arm: decls, assignments, call args, struct-literal
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fields, struct constants, globals.
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**Behavior change:** `examples/0300-closures-lambda.sx` passed `133` to an
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`s3` param and pinned the wrapped `-3`; updated to a fitting value.
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**Regression tests:** `examples/1156-diagnostics-int-literal-out-of-range.sx`
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(both faces diagnosed in one run) and
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`examples/0174-types-int-literal-boundaries.sx` (extreme in-range values,
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width-64 types, `xx`/`cast` escapes, call args).
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**Found during the fix:** negated-literal GLOBAL initializers (`g : s64 = -1;`)
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are rejected as non-constant — pre-existing gap, filed as issue 0113.
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---
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# 0112 — out-of-range int literal silently wraps into a narrower annotated target
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**Symptom.** An integer literal that does not fit its explicitly-annotated
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integer target truncates with no diagnostic: `x : s8 = 300;` binds 44,
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`y : u8 = 256;` binds 0. Expected: a compile-time error (the value is known
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exactly at compile time; this is the integer analogue of the float→int
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narrowing rule, which errors on non-exact `y : s64 = 1.5`).
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Split from issue 0111 (whose fix removed the *implicit* narrowing — an
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unannotated `x := 0` no longer adopts the fn return type — but the explicit
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annotation path keeps wrapping).
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## Reproduction
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```sx
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#import "modules/std.sx";
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main :: () {
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x : s8 = 300;
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print("x: {}\n", x);
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y : u8 = 256;
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print("y: {}\n", y);
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}
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```
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- **Observed** (current master): prints `x: 44` / `y: 0`, exit 0, no
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diagnostic.
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- **Expected**: compile error per literal, e.g.
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`integer literal 300 does not fit in s8 (range -128..127)`, and the analog
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for `256` / `u8 (range 0..255)`.
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Repro co-located: `issues/0112-int-literal-out-of-range-silent-wrap.sx`
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(unpinned until fixed).
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## Root cause (suspected area)
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`src/ir/lower/expr.zig` `.int_literal` arm (~1499): when `target_type` is an
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integer type, it emits `constInt(lit.value, tt)` with no fits-check — the
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value truncates at LLVM emission width. The annotated-decl path
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(`lowerVarDecl` with `type_annotation`, `src/ir/lower/stmt.zig` ~255) sets
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`target_type` to the annotation before lowering the initializer, so every
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annotated narrow decl funnels through this arm. Assignments to narrow
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lvalues (`b = 300` where `b: s8`) reach the same arm via `lowerAssignment`'s
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LHS-derived target and likely need the same check.
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## Investigation prompt (paste into a fresh session)
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> Fix issue 0112: an int literal that does not fit its integer target type
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> silently wraps. In the `.int_literal` arm of `lowerExpr`
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> (`src/ir/lower/expr.zig` ~1499), before adopting an integer `target_type`,
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> range-check `lit.value` against the target's signedness/width (the type
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> table knows both; mirror the bounds logic used by
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> `TypeResolver.integerLimitFor`). On overflow emit a diagnostic via
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> `self.diagnostics.addFmt(.err, node.span, ...)` naming the literal, the
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> type, and its range — do NOT silently fall back to s64 (REJECTED PATTERNS:
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> no silent fallback defaults); still return a `constInt` of the target type
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> so lowering continues to surface further errors. Audit sibling literal
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> sinks that bypass this arm (comptime folds, `lowerStructConstant`, global
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> initializers) for the same check.
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>
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> Verify: `issues/0112-int-literal-out-of-range-silent-wrap.sx` errors with
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> two diagnostics (s8/300, u8/256); boundary values still compile
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> (`x : s8 = -128` / `127`, `y : u8 = 0` / `255`, `m : u64` large literals).
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> `zig build && zig build test && bash tests/run_examples.sh` — any example
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> that relied on silent wrapping must be reviewed individually. Promote the
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> repro per the resolution flow (likely `examples/11xx-diagnostics-...`).
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